An image may be projected via a projector onto a projection surface assuming varying levels of reflectance or a patterned projection surface, with inconsistent illumination provided at the projector, or with the illumination conditions in the surrounding environment significantly affecting the projected image. Under such circumstances, the pattern or the irregularities on the projection surface will be superimposed over the projection image and thus the projection image will not be properly displayed. Patent reference 1 discloses a technology for correcting a projection image by photographing the projection surface and adjusting the dynamic range of the projection image to a range equal to or less than the lowest brightness within the photographed projection surface image, in order to cancel out the adverse effect of the non-uniform illumination and the like and thus enable accurate display of the projection image. Patent reference 1: Japanese Laid Open Patent Publication No. 2004-158941